Hydraulic lash adjusting device



Dec. 29, 1964 D. B. GREEN 3,163,158

HYDRAULIC LASH ADJUSTING DEVICE Filed April 2, 1964 2 Sheets-Sheet lfig. 1.

DEREK B. GREEN Inventor Home ys Dec. 29, 1964 D. B. GREEN 3,163,153

HYDRAULIC LASH ADJUSTING DEVICE Filed April 2, 1964 2 Sheets-Sheet 2 r II DEREK BGREEN venlor ttorneys United States Patent C) 3,163,153HYDRAULEE LASH ADEUSTING DEVMJE Derek B. Green, Four Oaks, England,assignor to Ford Motor Company, Dearhorn, Mich, a corporation ofDelaware Filed Apr. 2, 1964, Ser. No. 356,757 7 Claims. (Cl. 1239tl)This invention relates to lash adjusting devices for the valve train ofan internal combustion engine and more particularly to sealed hydrauliclash adjusting devices.

The use of hydraulic tappets to eliminate lash in the valve train of aninternal combustion engine is well known. Although the hydraulic tappetsfound in conventional engines differ in structural details, they allrely upon the engine lubricating system for a source of actuatinghydraulic fluid. Because the conventional hydraulic tappet uses enginelubricating oil as an operating medium, tappet failures may be caused bycontaminates contained by the lubricating oil or by chemical action ofthe lubrieating oil upon the tappet.

It has been proposed to provide a sealed hydraulic lash adjusting devicethat has a self-contained operating liquid. The most desirable liquidmay then be chosen, and foreign matter will not become entrapped withinthe tappet.

It is the principal object of this invention to provide an improved,self-contained hydraulic lash adjusting device for the valve gear of aninternal combustion engine.

An internal combustion engine embodying this invention comprises acamshaft and a valve train for transmitting motion from the camshaft toan engine poppet valve. The valve train includes a sealed hydraulic lashadjusting device comprising a body member and a plunger supported forreciprocation by the body member. First and second cup-shaped membersare positioned within the body member and divided by a disc to providefirst and second fluid chambers. Means are provided to permit fluidcommunication between the fluid chambers. The cup-shaped members havelongitudinally spaced, transversely extending flexible walls. One of theflexible walls engages the plunger. The other flexible wall is engagedby a spring-biased member that tends to deform the flexible wall anddecrease the volume in the associated fluid chamber to drive fluid intothe other fluid chamber and deform its flexible wall. The deformation ofthe flexible wall causes axial movement of the plunger in a firstdirection relative to the body member. Check valve means are providedfor precluding the flow of fluid between the fluid chambers uponmovement of the plunger in a second axial direction relative to the bodymember.

Further objects and advantages of this invention will become moreapparent when considered in conjunction with the accompanying drawings,wherein:

FIGURES 1-3 are cross-sectional views through 'a sealed hydraulic lashadjusting device, showing a first embodiment of the invention. The viewsillustrate the position of the parts of the lash adjusting device duringdifferent stages of operation.

FIGURE 4 is a cross-sectional view of the upper portion of a hydrauliclash adjusting device, showing a second embodiment of the invention.

FIGURE 5 is a cross-sectional view, in part similar to FIGURES 1-3,showing another embodiment of the invention.

Referring now to FIGURES 1 to 3, the illustrated tappet comprises acasing 1 formed of two parts 3 and 5. An internal bore of the upper part3 has a pair of shoulders 7 and 9 and an internally threaded lower section. The lower part 5 screws into the lower section and has a flange 11which is slightly spaced from the lower ice end of the threaded section.The upper end of the lower part 5 is spaced from the shoulder 9 so as toform a recess 13. The casing 1 is slidable in a bore (not shown) in anengine cylinder block, and its base is engaged by a conventional cam 15on a camshaft (not shown).

A sealed liquid chamber is formed by two cups 17 and 19 each having outturned rims 21 which project into the recess 13 and which are spacedfrom each other by a resilient diaphragm 23 and a rigid plate 25. Thediaphragm 23, which in its unstressed condition is planar, has a centralaperture 27. The plate 25, which has a concave upper surface, has twoapertures 29. The upper cup 17 forms a valve train compartment 31, andthe lower cup 19 forms a reservoir compartment 33.

A piston 34 having a convex upper surface is slidable in the lower part5 of the casing and is forced upwardly into engagement with a flexiblelower Wall of the lower cup 19 by a clearance coil spring 35 compressedbetween the piston and base of the casing. The spring 35, acting onpiston 34 exerts a less effective force on the associated engine poppetvalve than the valve spring (not shown) exerts on the associated enginepoppet valve when the latter is in its closed position. A channel 37connects the part of the casing 1 beneath the piston 34 with atmosphere.

A plunger 39 which engages a conventional push rod (not shown) isslidable in the upper part 3 of the casing and has a shoulder 41 and aconvex lower end which is engaged by a flexible upper wall of the cup17. The shoulder 41 radially overlaps but is axially spaced from theshoulder 7 of the casing upper part 3.

The tappet functions as follows. When the component parts of the valvetrain contract when the engine is stopped (FIG. 3), the spring 35 forcesthe piston 34 upwardly to contract the reservoir compartment 33 and soforce liquid from the latter compartment through the apertures 2? and 27in the plate 25 and diaphragm 23 respectively to expand the valve traincompartment 31. This forces the plunger 41 upwardly into contact withthe push rod to take up any clearances. The coil spring 35 also actsupon the piston 34 to decrease the volume in the reservoir compartment33 when the engine is running and the engine poppet valve is closed.Liquid will be driven from the reservoir compartment 33 through theapertures 29 and 27 into the vale train compartment 31 to cause theflexible Wall of the cup 17 to deform upwardly and move the plunger 39 asuflicient amount to eliminate clearance in the system.

When the component parts of the valve train expand (FIG. 1), the valvetrain compartment 31 is contracted by the push rod and liquid is forcedout of the latter compartment through the apertures 27 and 29 into thereservoir compartment 33 which is therefore expanded. The expansion ofthe latter compartment forces the piston 34 downwardly against theaction of the clearance spring 35.

When the engine is operating through the normal speed range and thetappet is being moved to open the valve (FIG. 2), the valve spring triesto contract the valve train compartment 31 and does in fact increase thepressure in the latter compartment. This increase in pressure causessome liquid to try to flow from the valve train compartment 31 throughthe apertures 27 and 29 into the reservoir compartment 33. Due to therestriction by the aperture 27 to this high rate displacement and beforeany appreciable amount of liquid can pass, the diaphragm 23 flexes intocontact with the concave surface of plate 25 to block communicationbetween the two compartments. Except at low speeds communication betweenthe two compartments is virtually blocked and the system will act as asolid tappet.

When the engine isoperating at low speeds and the tappet is being movedto open the valve, the valve spring is desirable.

tries to contract the valve train compartment 31 and does in factincrease the pressure in the latter compartment. This fairly slowincrease in pressure first causes the liquid to fioW from the valvetrain compartment 31 into the reservoir compartment 33. The restrictioncaused by the aperture 27, however, causes the diaphragm 23 to flex intocontact with the convex surface of the plate 25 to block communicationbetween the two compartments. The time effect of the low pressure lossthrough the aperture 27 results in a small amount of lost motion in thevalve train, so that the valves open slightly late at low speeds, whichAt high operating speeds the pressure difference across aperture 27 issuch that very little liquid is able to flow through the aperture 27during opening of the valve. Consequently there is very little lostmotion in the valve train. By selecting proper sizes of the apertu-re 27in the diaphragm 23, the degree of late opening of the valves at varyingspeeds may be adjusted.

In the tappet shown in FIGURE 4, the plunger 39 is replaced by a ball42, and the push rod 43 has a part spherical surface which engages theball 42. In all other respects the tappet is identical to that shown inFIGURES 1 to 3.

In the tappet shown in FIGURE 5 there are two difierences from thetappets shown in FlGURES l to 4. Firstly the rims-21 of the cups arebent around the plate 25; and secondly the plunger 39 has a secondshoulder e5 which radially overlaps the upper part 3 of the casing. Theshoulder 45 ensures that the valve is opened if the liquid in the valvetrains compartment 31 should escap The tappet then functions as anormal, solid tappet with cold clearance.

The tappets shown and described are exemplary only of preferred formsthe invention may take. The tappets also may be positioned at anyconvenient location within the valve tnain and may be used inconjunction with an overhead camshaft valve gear. Other changes andmodifications may be made without departing from the spirit and scope ofthe invention, as defined by the appended claims.

-I claim:

1. An internal combustion engine comprising a camshaft and a valve trainfor transmitting motion from said can shaft to an engine poppet valve,said valve train including a sealed hydraulic lash adjusting devicecomprising a body member, a plunger supported for reciprocation by saidbody member, a disc contained Within said body member, a firstcup-shaped member supported within said body member on one side of saiddisc to define a first fluid chamber therewith, a second cup-shapedmember contained within said body member on the other side of said discto define a second fluid chamber therewith, each of said cupshapedmembers having axially spaced ilexible Walls extending transversely tothe longitudinal axis of said body member, means providing fluidcommunication between said fluid chambers, said plunger being inengagement With the flexible Wall of said first cup-shaped member, aspring-biased member in engagement with the flexible wall of said secondcup-shaped member for deforming said flexible wall to decrease thevolume in said second fluid chamber and urge liquid into said firstfluid chamber for deforming the flexible wall of said first cupshapedmember to urge said plunger in a first axial direction relative to saidbody member, and check valve means for resisting liquid flow from saidfirst fluid chamber to said second fluid chamber upon deformation of theflexible Wall of said first cup-shaped member by movement of saidplunger in a second axial direction relative to said body member.

2. An internal combustion engine as defined by claim 1 wherein means areprovided to positively limit the movement of the plunger in the secondaxial direction relative to the body member.

3. An internal combustion engine comprising a cam shaft anda valve trainfor transmitting motion from sai tin camshaft to an engine poppet valve,said valve train including a sealed hydraulic lash adjusting devicecomprising a body member, a plunger supported for reciproccp tion bysaid body member, a disc contained Within said body member, a firstresilient member supported Within said body member on one side of saiddisc to a first expansiblc fluid chamber therewith, a second resilientmember supported Within said body member on the other side of said discto define a second cxpansible fluid chamber therewith, said disc havinga concave surface facing said first fluid chamber, a fluid passageextending from said concave surface through said disc to said secondexpansible fluid chamber for fluid flow between said chambers, a plungerin engagement W'"h first resilient member, means biasing said secondremlient member in a direction to decrease the volume in said sec- 0ndexpansible fiuid chamber and urge fiuid therefrom into said firstexpansible chamber for urging said plunger in a first axial directionrelative to said body member, a flexible diaphragm positioned acrosssaid disc adjacent said concave surface, said diaphragm being deformableinto engagement with said concave surface upon an increase in pressurein said first expansible fluid chamber to close the fluid passage insaid disc and prevent fluid flow into said second expansible fiuidchamber, and a restricted fiuid passage in said diaphragn 4. An internalcombustion engine conrising a camshaft and a valve train fortransmitting motion from said camshait to an e C no poppet valve, saidvalve train including a sealed hydraulic lash adjusting devicecomprising a body member having a longitudinally extending bore therein,a plunger supported for reciprocation in an open end of said bore, adisc extending transverse across said bore, a first cup-shaped memberhaving a cylindrical section engaging said bore and terminating at oneend adjacent one side of said disc, said cylindrical section terminatingat its other end in a resilient Wall extending transversely across saidbore and defining a first fiuid chamber with said disc, a secondcup-shaped member having a cylindrical section engaging s id bore andterminating at one end adjacent the other side of said disc, the otherend of tr e cylindrical section of said second cup-shaped memberterminating in a resilient wall extending transversely across said boreand defining a second fiuid chamber with said disc, fiuid passage meansextending through said disc for fluid flow between said fiuid chambers.said plunger having a convex surface in engagement with the resilientWall of said first cup-shaped member for deforming said resilient Walland decreasing the volume in said ii at fluid chamber upon movement ofsaid plunger in a first axial direction within said bore, aspring-biased member having a convex surface in engagement with theresilient Wall of said second cup-shaped member for deforming said walland decreasing the volume in said second fluid chamber to induce fiowinto said first fluid chamber and move said plunger in a second axialdirection Within said bore, and check valve. means in said fiuid passagemeans for restricting fluid flow from said first fluid chamber into saidsecond fiuid chamber upon movement or said plunger in said first axialdirection.

5. An internal combustion engine as defined by claim 4 wherein means areprovided on the plunger to coact with means on the body member topositively limit movement of said plunger relative to said body memberin the first axial direction.

6. An internal combustion engine comprising a cam shaft and a valvetrain for transmitting motion from said camshaft to an engine poppetvalve, said valve train including a sealed hydraulic lash adjustingdevice comprising a body member having a longitudinally extending boretherein, a plunger supported for reciprocation in an open end of saidbore, a disc extending transversely across said bore, a first cup-shapedmember having a cylindrical section engaging said bore and terminatingat one end adjacent one side of said disc, said cylindrical sectionterminating at its other end in a resilient wall extending transverselyacross said bore and defining a first fluid chamber With said disc, asecond cup-shaped member having a cylindrical section engaging said boreand terminating at one end adjacent the other side of said disc, theother end of the cylindrical section of said second cup-shaped membererminating in a resilient Wall extending transversely across said boreand defining a second fluid chamber with said disc, said disc having aconcave surface facing said first fluid chamber, a fluid passageextending from said concave surface through said disc to said secondfluid chamber of fluid flow between said chambers, said plunger having aconvex surface in engagement with the resilient Wall of said firstcup-shaped member for deforming said esilient Wall and decreasing thevolume in said first fluid chamber upon movement of said plunger in afirst axial direction Within said bore, a spring-biased member having aconvex surface in engagement with the resilient wall of said secondcup-shaped member for deforming said Wall and decreasing the volume insaid second fluid chamber to induce flow into said first fluid chamberand move said plunger in a second axial direction Within said bore, aflexible diaphragm positioned across said disc adjacent said concavesurface, said diaphragm being deformable into engagement with saidconcave surface upon an increase in pressure in said first fluid chamberto close the fluid passage in said disc and prevent fluid flow into saidsecond fluid chamber, and a restricted fluid passage in said diaphragm.

7. An internal combustion engine comprising a camshaft and a valve trainfor transmitting motion from said camshaft to an engine poppet valve,said valve train including a sealed hydraulic lash adjusting devicecomprising a first body member having a first bore extendinglongitudinally from one end thereof, a second bore extendinglongitudinally from the other end of said first body member andterminating adjacent said first bore at a shoulder, a second body memberhaving an outer surface in engagement with said second bore andterminating at a shoulder that is axially spaced from the shoulder ofsaid first body member, a third bore in said second body member, a firstcup-shaped member having a cylindrical section engaging said first boreand terminating at one end in a flange portion in engagement with theshoulder of said first body member, said first cup-shaped memberterminating at its other end in a resilient Wall extending transverselyacross said first bore, a resilient diaphragm extending transverselyacross said one end of said first cup-shaped member and being inengagement around its outer periphery With said flange portion, asubstantially rigid disc positioned adjacent said resilient diaphragmand having a convex surface facing said diaphragm, a second cup-shapedmember having a cylindrical section engaging said third bore andterminating at one end in a flange portion, said flange portion being inengagement at one side with said disc and at the other side with theshoulder of said second body member, the other end of said cylindricalsection of said second cup-shaped member terminating in a resilient Wallextending transversely across said third bore, said first cup-shapedmember and said resilient diaphragm forming a first fluid chamber, saidsecond cup-shaped member and said disc forming a second fluid chamber,fluid passage means extending through said disc, said resilientdiaphragm being deformable upon an increase in fluid pressure in saidfirst chamber to engage said concave surface of said disc and close saidfluid passage means, an orifice in said resilient diaphragm for limitedfluid flow therethrough, a plunger supported for reciprocation in theopen end of said first bore, said plunger having a convex inner surfacein engagement with the resilient Wall of said first cup-shaped memberfor deforming said resilient wall and decreasing the volume of saidfirst fluid chamber upon movement of said plunger in a first axialdirection in said first bore, and a spring-biased member positioned insaid third bore, said spring-biased member having a convex surface inengagement with the resilient Wall of said second cup-shaped member fordeforming said Wall and decreasing the volume in said second fluidchamber.

References Cited in the file of this patent UNITED STATES PATENTS

1. AN INTERNAL COMBUSTION ENGINE COMPRISING A CAMSHAFT AND A VALVE TRAINFOR TRANSMITTING MOTION FROM SAID CAMSHAFT TO AN ENGINE POPPET VALVE,SAID VALVE TRAIN INCLUDING A SEALED HYDRAULIC LASH ADJUSTING DEVICECOMPRISING A BODY MEMBER, A PLUNGER SUPPORTED FOR RECIPROCATION BY SAIDBODY MEMBER, A DISC CONTAINED WITHIN SAID BODY MEMBER, A FIRSTCUP-SHAPED MEMBER SUPPORTED WITHIN SAID BODY MEMBER ON ONE SIDE OF SAIDDISC TO DEFINE A FIRST FLUID CHAMBER THEREWITH, A SECOND CUP-SHAPEDMEMBER CONTAINED WITHIN SAID BODY MEMBER ON THE OTHER SIDE OF SAID DISCTO DEFINE A SECOND FLUID CHAMBER THEREWITH, EACH OF SAID CUP-SHAPEDMEMBERS HAVING AXIALLY SPACED FLEXIBLE WALLS EXTENDING TRANSVERSELY TOTHE LONGITUDINAL AXIS OF SAID BODY MEMBER, MEANS PROVIDING FLUIDCOMMUNICATION BETWEEN SAID FLUID CHAMBERS, SAID PLUNGER BEING INENGAGEMENT WITH THE FLEXIBLE WALL OF SAID FIRST CUP-SHAPED MEMBER, ASPRING-BIASED MEMBER IN ENGAGEMENT WITH THE FLEXIBLE WALL OF SAID SECONDCUP-SHAPED MEMBER FOR DEFORMING SAID FLEXIBLE WALL TO DECREASE THEVOLUME IN SAID SECOND FLUID CHAMBER AND URGE LIQUID INTO SAID FIRSTFLUID CHAMBER FOR DEFORMING THE FLEXIBLE WALL OF SAID FIRST CUP SHAPEDMEMBER TO URGE SAID PLUNGER IN A FIRST AXIAL DIRECTION RELATIVE TO SAIDBODY MEMBER, AND CHECK VALVE MEANS FOR RESISTING LIQUID FLOW FROM SAIDFIRST FLUID CHAMBER TO SAID SECOND FLUID CHAMBER UPON DEFORMATION OF THEFLEXIBLE WALL OF SAID FIRST CUP-SHAPED MEMBER BY MOVEMENT OF SAIDPLUNGER IN A SECOND AXIAL DIRECTION RELATIVE TO SAID BODY MEMBER.